Surface treatment refers here to a layering process where a surface layer of a substrate is modified by allowing particles to diffuse in the substrate matrix, or where particles are deposited on the surface such that a coating is produced on the substrate. Particles used for this kind of surface treatment are typically very small, the size distribution ranging from 10 to 100 nm. Particles of this size are generally referred to as nanoparticles. Nanoparticles are generated in a particle synthesis process where precursor chemicals are exposed to a thermal reactor. In the intense heat of the thermal reactor they undergo specific thermochemical and physical reactions that lead to synthesis of desired particles.
In industrial applications, the particle synthesis process typically incorporates a source element that applies a nozzle for ejecting a combination of precursor substances for surface treatment particles, and a thermal reactor for transforming the combination of precursor substances to a directed particle flow. Typically the thermal reactor is a turbulent hydrogen-oxygen flame into which the nozzle outlet channels from one or more nozzles feed materials, either mixed together or through separate outlets.
Conventionally the surface treatment implementations have been strictly focusing to direct impact areas where the flow of nanoparticles is directed against the treated surface rectilinearly. Particle flow effects outside direct impact areas have been considered as residue and various measures have been applied to effectively eliminate these effects from industrial surface treatment processes. This conventional approach is, however quite ineffective, since a considerable amount of particles does actually not end up in the treated surface, but is removed with carrier gases away from the process atmosphere. This manifests as poor yield and added efforts for cleaning the contaminated process atmosphere.